Tuning

In progress...largely unedited

Tuning is one of those subjects that is in the eye of the beholder and can be considered to be an extremely simple subject, or an extremely complex one.  It depends upon the experience of the tuner and the depth to which he wishes to pursue the subject.

Serious racers can go quite deep.  To demonstrate this, I am going to include a post made by Tim Stockwell about three years ago when doubt was expressed over Tim's running into the tens with a stock long block in the early days of the Turbo Buick when such things were considered impossible. 

The post by Tim came from this thread 

 http://www.turbobuicks.com/forums/showthread.php?s=&threadid=3947&highlight=stockwell

"Hello all...........I guess it is time for me to chime in. First off, I would like to say to those non-believers including Joe (that has always had a problem with this) that I did go to extreme measures to prove this cars capabilities. As we all remember, the car was published in the GSX-TRA numerous times and was even run at Norwalk with at least 15 witnesses and taken directly to Red Armstrong's house and torn down, and video recorded by Paul with all of the witnesses there. You have to remember that I have been racing for many years, this car was not a daily driver and I wasn't afraid to push it to see just how far it would go. True, Red being so close definatley played a big part in this. He made many diferent chips and helped a great deal in this "experiment". There was no "voodoo" or anything here, just a lot of tuning and small details that many overlook. For example, how many of you index your spark plugs? How many of you adjust your brakes for less drag? How many of you loosly adjust your wheel bearings? How many of you loosly adjust your front control arms? How many of you use thin grease on your front wheel bearings? How many of you run 60 psi in your front tires? How many of you get your front end aligned for drag racing purposes so the front tires don't scuff under acceleration? The list goes on...........it is nothing special, just what racers have done for years. I am a person that "sweats the deatails", so to speak and I would do anything no matter how small if it made sense and could possibly help. I did run as fast as 11.62 with a stock turbo and intercooler, and I did go as fast as 10.76 with a never opened up motor or transmission, and a stock D-5 converter............there were too many people there that saw it, and know me, to call liars. I did get out of the Buick scene because so many guys were so immature and jealous that they didn't do this too, but I am back. During this 5 year span my wife and I have built a beautiful new home, and are expecting our first child in March........there is more to life than cars. I currently have 3 TR's and am still looking for the "right" one to do my old combo with. Another note, when I tore my white car down, all of my bolt on parts went on my fathers 86K mile GN and it went as fast as 11.12 before he sold it. Another local guy nere (Bob Bashoor) followed my recipe to the tee, except for no rear suspension mods and went 11.03 with a 1.56 60 ft.........take his e.t and my suspension and 1.44 60 ft. and what do you have? My guess would be in the 10.80's all day long. This isn't brain surgery here, just simple facts, patience, and not being afraid to push the envelope.......................Tim Stockwell "QWIK-T"

If you are interested in reading about Tim's build up and the progression he made, go here-

 http://www.gnttype.org/techarea/recipes/Stockwell.html

It's amazing how simply it was done back in 1995/96.

I put the above in in an attempt to demonstrate the breadth that tuning can cover.  It can be far more than sticking a chip in the ecm and playing with the fuel pressure.

Being old school and having spent considerable time at the track playing with various types and brands of cars for far too many years, I prefer to take a broad based approach seeking synergy from the parts.  I am going to try to stick to the basics rather than delving too deep into the theory.  There are so many ways to approach the various systems that I shall hopefully leave you with an understanding and you can fill in the blanks in the way most suitable to you.

Try to learn the difference between theory, empirical results, opinions, and magazine articles.  What follows is my opinion based upon my own experience and that of others.  I will try to be somewhat general in nature as I understand there is usually more than one way to approach a problem.  There is no substitute for experience as long as one is willing to do some testing to ascertain what works best for ones specific combination.  Don't fall for magic numbers or magic parts.

Don't try to compare your car against another car with a different combination running on a different day on a different track with different weather conditions at a different altitude, etc.  It will drive you crazy and mean virtually nothing.  Takes a lot of analysis to normalize car under such conditions.  If you are that good, you should be betting on horses down at the horse track. 

Rear Suspension

What does the rear suspension have to do with tuning?  It's quite simple.  If you cannot transfer power to the pavement, you cannot go quick(ly).  With good running cars, the one that spins the most, loses most often.

On an average 11 - 12 sec car, a reduction in the 0-60 ft times of one tenth generally equates to one and a half tenths at the lights.  A quicker car may pick up closer to two tenths at the lights.  See why obtaining the best "hook" is so important?

Part of getting the best short times is obviously in driving skill.  The other half of the equation is setting the car up so that it is easy to drive.

I am not going into detail on suspension theory.  An excellent book that covers the subject in great detail, yet, in simple English, is Dave Morgan's "Door Slammers-The Chassis Book".  Dave used to write the column on suspension in National Dragster and is now employed by the IHRA.  He tours and puts on suspension clinics periodically.  Excellent software that allows one to calculate all needed parameters is "4 Link Calculator" by Performance Trends.

Now, the factory suspension was not designed with drag racing in mind.  It was designed for good ride and intended to keep the rear axle more or less located under the car.  On cars that sit at factory ride height, the instant center obtained by projecting lines thru the upper and lower control arms and determining the intersection part is often either behind the car, which is terrible for planting the rear tires optimally, or way to the front of the car-again, very bad for weight transfer.

In spite of the bad location, these cars will still hook surprisingly well using the factory control arm locations.  Short times (0-60ft) of 1.6-1.7 seconds are not at all uncommon for 11-12 second cars.  Cars that go even faster routinely have the power to go 1.4-1.5 seconds in the 0-60 ft light.

What does it take?  It takes good bushings in the control arms-all four bars, both ends.  Although I prefer rubber bushings, I think the polygraphite bushings probably do a better job when it comes to drag racing launches-at least in theory.  They are cheaper as well.

Lower Control Arms-Boxing the lower control arms prevents distortion when they are under compression from launch.  This is more important when very sticky tires, or, slicks are used.  The upper arms are under tension during acceleration and are not likely to suffer dynamic distortion.  Box the lowers.  They will perform better when you get quicker and will not distort with heavier sway bars installed.  If you don't wish to box your own...there are plenty of options out there.  Basically, they are all the same no matter the hype.

Do you need adjustable upper arms?  That really depends upon how fast your car is.  If it runs in the tens, adjustable upper arms allow you to add some negative pinion angle which may help transfer power a bit better on a hard launch and aid in avoiding some driveline bind.  One can obtain the same effect by buying a set of lower control arms from Paul Ferry of HRpartsNStuff that are 0.5" longer and which will normally provide a couple of degrees of negative pinion angle which is fine for a street car.  Cars that run in the tens, or better, may benefit from 4-6 degs of negative pinion angle, but, this amount will wear the rear U-joint out quickly in a daily driver.  I prefer Paul Ferry's adjustable uppers and leave lower stock length. Set angle to 3 deg.

If you have access to four wheel scales, then you can use the adjustable upper arms to dial some preload into the passenger side rear tire by shortening the arm slightly.  Read Dave Morgan's book before you start...

Remember, if you install upper control arms with solid bushings in the front, the frame will need to be reinforced, or, you will soon find yourself with elongated mounting holes as the stock frame simply cannot stand the abuse.

Do you need a long pinion snubber?  Just say no.  Long snubbers were in vogue on leaf spring cars back in the '60s on 7 liter Super Stock cars that tended to wrap the rear axle up in the spring on launch.  On a coil spring rear suspension with four link control arms, the rear housing does not rotate much if the bushings are good.  Further, they do little for load transfer as they press down on the pinion nose in the center rather than over the passenger side end which tends to lift upon acceleration.  Worst case, they load the rear axle and then unload it up in the top end of first gear causing wheel spin and/or a change of direction of the car.  Yes, I know, lot's of us old guys tried them initially, but, we were wrong.  Save your money.

Do you need air bags?  That is a definite Maybe. 

The primary function of an air bag is to increase loading on the passenger side rear tire to counteract the natural unloading, and resultant tire spinning, that is incurred when torque lifts the rear right side of the axle and removes wait from that tire.  Wait, you say, that is why we have posi-traction rear units-they apply power to both tires.  Not exactly, they transfer power to the tire that has the most traction...in this case, the driver's side tire.

A secondary function of air bags may be to prevent the body from sitting down and cutting the rear tires if large tires that don't tuck completely into the fender wells are employed.

Either way, the air bags function by increasing the spring rate of the rear coil springs.  The more air that is added to the bags, the stiffer the springs become.  This is not necessarily desirable as the rear axle becomes increasingly less compliant as the spring rate is stiffened (increased) and may reach a point where excessive tire spin at launch results or the load transfer from launch does not last long enough and the tires break loose shortly after launch.

Now, if we examine the primary function of an air bag installation which is to increase the load on the passenger rear tire, we note that as air bag pressure is increased on this side of the car, the body is jacked up higher into the air which in turn increases the load on this tire at launch (and removes it from the other tire).  This makes it harder for the axle to lift up and reduce traction on this tire.

If we are only trying to equalize launch traction, there is no real reason to use two air bags as one on the passenger side will suffice.  On a posi equipped vehicle, 10# of pressure in the bag may be sufficient to do the job.  On a peg leg car (non-posi) it may take 20-30# to do the job.  Hopefully, it should be obvious that the more powerful the engine, the more the torque roll will be and the more the bag will need to be inflated.

How do we determine a starting pressure for the air bag?  There are two simple methods.

Do a burn out....the two strips of rubber left on the pavement should be the same length.  Add air to the passenger side bag until the two strips are equal.

The second method entails loading the car to the normal launch boost against the brakes and adjusting the air in the bag(s) until the rear bumper is parallel to the ground at launch boost.  Note that this technique does not work on tranny braked cars and is hard on the tranny due to rapid heat build up so the boost should not be held more than a few seconds.  The first may not seem to be as precise, but, I suspect it is the only viable means as it accounts for the dynamics of launch as well as static conditions.

Let's retrace our steps a bit and consider a few things. 

The more power the car makes, the more it will tend to unload the rear passenger side tire.  Hence more air will be required.

Increasing the effective spring rate will improve the traction at launch by making both tires do equal work, but, it may affect handling at high speed as the body is torqued due to bag pressure and imperfections in the strip can be magnified.

Increased spring rate may not be desirable for maintaining traction throughout the run as the increased rate resists load transfer and the tires may unload prematurely causing wheel spin up in the top of first gear or into second.  Typically, softer spring rates help cushion the blow delivered at launch by stick shift cars or by tranny braked automatics that leave violently.  Stiffer spring rates may benefit automatics that leave on the foot brakes, but, note that the stock springs may be considered stiff as they are.

Considering the above, it would be desirable to minimize the amount of air used in air bags, or, to eliminate them altogether.

How to do that provides a segue into sway bars.

Aren't sway bars only good for going around corners?  Absolutely NOT!  Sway bars are more properly called anti-roll bars as they assist the body in maintaining a level attitude in relation to the road.  The effort to do so also resists the effort of the rear axle to lift the passenger side rear tire off the ground and into the wheel well which allows tire spin.  The factory supplied rear sway bar is undersized even for good handling as it allows too much understeer, and, it is definitely undersized for drag racing purposes.  When using the factory rear bar, air bags definitely provide some traction benefits at the track.  That is why I stated that air bag need is a definite maybe in the prior section. 

If the factory bar is replaced with a substantially larger bar such as the ATR bar which is a massive 1.375" in diameter as compared to the factory unit which is a little less than 1.0" in diameter, there is a large  increase in the resistance provided to the rear axle as it tries to twist under launch torque.  In this case, an air bag may not be required, or, it may need far less air to equalize "bite" from both tires.

For informational purposes, it is worth noting that there is an alternative to the factory style mounted rear bar style.  The Wolfe Racing bar works very well for very serious cars and should reduce the handling problems that are often inherent with very quick cars.  It is both expensive and a  pain to install as it requires welding and may interfere with the exhaust system.  It may also cause bind during cornering on street cars.  The HRPartsNStuff bar is similar in design concept but is a bolt in solution made precisely for our cars, and, it should not bind.  One of these days, I intend to install one on my GN in place of the ATR bar.  Look at the links for the difference in concept and additional theory.  I suspect that cars running in the nines, or faster, will show more benefit from a performance versus cost stance than most of us will see with our cars. 

Bottom line-the rear sway bar is a major contributor in obtaining maximum traction and the stiffer it is, the less air bags, and their possibly negative effects, are needed.

Note.   Wolfe bars are not really streetable!

Rear Shocks-How important are they?  Well, you need at least two of them.  That is not as facetious as it might sound.  Shocks, at least on cars that are slower than 11.0 are not particularly critical.  I would say that a pair of worn out stock shocks would do very well while a set of good, stiff shocks such as Bilsteins would not be very good from a technical view.  If you want to have something that will work well and be a good conversation piece, put a pair of QA1 adjustables on the back and set them to soft for the track and up in the mid range for normal driving.  Don't know if you will see any difference, but, it looks cool to crawl under there and turn the knob!  If you have a hard leaving car running down in the tens, a set of specialty drag shocks would be good for the strip, but, not very suitable for a daily driver.  Whatever shocks you have on the rear now should work well unless they are rusted solid and don't let the rear end sit down under acceleration.

Rear Springs-Do you need special drag racing springs to get a good launch?  Again, I think this is one of those non-critical items.  The factory springs should work well at least into the nines.  Considering that most of us are using our cars on the street to some extent, I think the springs that are sold by Moroso and others as specialty drag springs are really not worth the effort.  All out racers launching at very high boost off a tranny brake might see a slight benefit of such combined with a set of rear drag shocks, but, I don't think it would be a major improvement, or even a significant one for most of us.

Note, stock Moog replacement springs have gone 1.3s so there is little, if any, bang for the buck with this type of spring replacement (special drag springs such as the Morosos)  and they may make the car unsafe in normal driving.

Tires-What to use?  In recent years, drag radials have been the trick to use for daily drivers that see week end action.  The BFG DRs were the first on the scene, but, they are a little more soft and have less tread than than the Nittos so they may not last more than 3000 miles and they can be exceedingly dangerous in the slightest rain.  The Nittos came out next and they are a bit harder and offer considerably better performance in the wet due to the tread design.  They seem to last closer to 10,000  miles for the average driver.  The latest, hottest tire is the Mickey Thompson drag radial which has a softer, stickier rubber and seems to be giving better short times than the competitors.  Being softer, they may not last that long for those that want to do burn outs after each stop, but, they may be the trick for those that are serious about it, or, are making more power where the other drag radials just want to spin.

M/T does not suggest them for anything other than dry pavement.  They appear perfect for a week end warrior on those nice, dry days.

The factory tire diameter was 26" which is only slightly taller than the average 275/50-15 tire.  A number of cars that are running 115 mph, or faster, seem to often prefer a taller tire in the 27'-28" class.  A 275/60-15 is normally 28" in diameter.  There are some cars which don't appear to like the extra height and I suspect it is all combination driven.

Most Drag Radials seem to like about 18 lbs of air.  It's a good starting place to find out what works best for you.  Remember that track surface, prep, temperature, and the boost you leave at will all affect pressure.  Don't use less than needed, if for no other reason than safety.

When doing burnouts...do the minimum required to make the tires sticky...usually staying in the water until the smoke changes from white to a slight bluish tint, and no longer, is about right, I think.  This brings the sticky to the surface without frying the tire.

Rear Suspension Summary-  If you are running 11.0's, or slower, I suspect that you will get about 85% of the possible improvement from a pair of boxed lower arms, good bushings in both uppers and lowers, a large sway bar, stock springs, stock, or similar, shocks and a sticky set of tires.  This can be done relatively cheaply and should provide adequate consistency for bracket racing.

If you want to address the other 15%, then adjustable uppers, relocated control arm mounting positions, a Wolfe/HRPartsNStuff style rear bar, and drag shocks can all help if you take the time to get everything dialed in correctly.  This means repeated testing with slight adjustments between runs.  There ain't no right way beyond what your car tells you it likes...no short cuts!

An air bag on the passenger side may help the final tweak as well.  Just remember that an air bag increases effective spring rates and that is probably not desirable so keep the pressure as low as possible to get an even burnout from both tires.  Two bags may be used if it helps eliminate tire rub, but, wheels with the right backspacing would be preferable.

Driveshaft loop-Yes you need one unless you have a death wish or just want to destroy your car.  Buy one, Install one!

Also, most tracks require it.

Front Suspension Set Up

Front end-What's it got to do with going quick?  The answer is "plenty"!  In order to get the best short times and the highest top speeds, the car has to transfer weight (mass) from the front end where about 58% of the weight resides to the rear tires at launch to provide maximum "hook" and then it has to allow the car to run straight all the way down the track with minimum rolling resistance.

Front Sway bar-should I remove it? At the track, definitely.  But, remember that this can make the car unstable if the steering wheel is suddenly moved, PARTICULARLY if you don't have the suggested large rear sway bar on the car.  If you do have the larger rear bar and larger rear tires, then, the car should handle fairly well and can be driven to and from the track with the bar removed.  I don't suggest autocrossing on freeway ramps, though. Remember that many things we do to improve drag racing performance may actually harm normal driving performance.  Be smart and be safe!

Removing the front bar will allow the front end to rise and add down force to the  rear tires which is what we want.  If you are serious about improving short times, this is a "must" change.

Removing the front bar will also be a weight saving gain in a area that helps with lift and load transfer.

Front Shocks-Do I need special shocks?  That depends upon how serious you want to be.  Stiff shocks like Bilsteins resist the front end lift and limit the mass shifted to the rear tires.  Specialty drag shocks like the 90/10s, or the 80/20s allow the front end to rise without much resistance so that mass is easily transferred to the rear tires, but considerable resistance is encountered when the front begins to settle.  This maintains the mass transfer as long as possible and may prevent the tires from beginning to spin after leaving the line.  These shocks are excellent for a race car but can make for a dangerous handling car on the street.

Some shocks, such as those made by Competition Engineering can be adjusted from 90/10 to 80/20 to 60/40.  The latter is more streetable, but, these shocks typically have to be removed and the rod turned to change the damping.

Other shocks, such as the QA1s have a knob on them to change from stiff to soft, but, I understand that this does not change the ratio of the shock.  This means the front will come up easily, and also go down easily.  Better than a set of Bilsteins, but, not as good as a true drag shock.

Do some searching on the Net.  There are quite a few articles on shocks and how to use them.  Better information than I can parrot, I am sure.

Front Springs-Do I need special drag springs?  I would not unless building a true race car.  After all, these cars should be fun to drive around corners as well as down the track.  The factory springs are not too stiff and work well with the aforementioned shocks.  If you have Eibachs, or similar, as I do, then you really need a good set of shocks that do not add resistance to the front end lift.  Stock springs are not a major deterrent until one is far into the nines, I suspect.

Alignment-Is there anything to consider here?  I would put plenty of positive castor in the front to encourage the car to run straight.  Always get a thrust alignment which references the front wheels to the rear wheels for minimum rolling resistance.  For a drag racing alignment, have the shop check the toe with the front end up in the air simulating a launch and adjust to reduce "scrub" in order to minimize rolling resistance.  Check the toe with the front down close to the static position, and, find a happy medium that does not interfere with normal driving. Toe on each side will probably be close to 1/32".  Camber should be close to "zero".

Front Tires-Should I get a set of skinny front runners?  Yes, if it is a pure drag car.  If you are going to drive them on the street, then consider the load ratings of the tires.  The average Regal has at least 1100 lbs on each front tire in a static position, and, this goes up considerably when the brakes are stomped.  Those skinny front tires may look cool to the teenaged vampires hanging around Sonic, but, they might kill you in the wrong usage.  Think about what it takes to be safe as well as what looks good to you, or whomever you are trying to impress.

When at the track, air them up to minimize rolling resistance.

Typical drag racer tricks-how serious should I get? That is really up to you.  If you want to take the tension off the control arm bushings, or use Del-alums. etc., then go for it.  Just don't forget this is for the track.  Tighten them back up before you go home.  If you want to use lightweight grease, loosen the wheel bearings, etc., again remember this is no good on the street.

The Frame

The Frame???  What the heck are you talking about?!  Yep, the frame!  Everything is bolted to the frame, and, it is extremely flimsy/flexible when abuse is applied.  Crawl under the car and examine it.  You will see that the frame is not completely boxed, but, is a C section in several areas and is also made of quite thin material.  If you remove the rear body bushings, you will see the frame rails sag downward.  Not very impressive in my eyes.

When the car is launched, the frame twists and becomes part of the steering system.  This does not lead to consistency.  The stronger the car leaves, the worse the problem.

Okay, what can we do to improve this situation?

1) Replace the body bushings at all positions, top and bottom, plus add the GNX bushings.  Doing so will incorporate the body as a strengthening member to the frame.  If you want maximum effect, there are poly bushings available.  Be warned that they may add some road noise into the car according to some.

2)  Add the triangle bracing to the front frame and install the cross bracing in the trunk.  The former stiffen the front half of the frame while the latter removes a lot of twist from the body which in turn, hold the frame in position.

3)  If the car is 11.50 or quicker, install a roll bar.  In addition to protecting you if you hit the rail, or roll it, at 120 mph, it ties the frame together which will make the car launch much straighter which may not only keep you from crossing the center line and killing the guy in the next lane, but, when the car goes straight, it gets to the other end quicker.

4)  You can also box the rails in the open areas to add some strength.  Worried about the additional weight?  hey, didn't you take the front sway bar off?

All in all, the frame is the foundation off which you work.  It determines the success of everything that you do to improve the drag "racibility" of your car. 

Transmissions

Rebuilt transmissions-Do I need to spend $2000.00 or more for a killer transmission?  If you are quicker than 11.5, or run slicks and like to do banzai, high boost, launches, yeah, you probably do.  If you don't fit this category, then something around half of that figure will probably meet your needs. 

If you are paying to have it rebuilt make sure the shop is  familiar with the HI-Per rebuilds that our Buicks require.

When you decide it is time to rebuild your tranny, it's a good idea to replace the converter or have it opened and cleaned out as it is probably full of trash and may be tired.  No since having it pumping trash back through your new tranny or failing and filling it with bits of metal.  If you have a newer unit, have it cut open and cleaned out.  This is particularly critical if your old tranny has given up the ghost.

Replace the stock transmission cooler. It will also be full of debris.

A well built tranny with a good converter and a good tranny cooler should perform the same each run of the day whether it is cold or hot.  It should not flare on shifts and it should not slip more on the top end from one run to the next.

How hard the tranny shifts is not necessarily an indicator as to the quality of how well the tranny is built.  It may impress your friends, but, all it may be doing is increasing the rate of wear on the drive train parts. One wants minimum slippage (flare) on the shifts, but brutal shifts may be do more harm than good.

When analyzing run differences, it is important to compare your data logs and see if the mph is consistent with rpm from run to run.  It's a waste of time trying to tune for problems that don't exist in the engine when the problem lies in the tranny.  Be sure you compare the rpm at the shifts as well as the rpm during the non shift periods of the run.

Converters-What should I buy?  Torque converters are kinda like religion; there is an option for everyone.

The stock converter was stamped D5 and was a 12" converter that stalled around 2200-2400 rpm at 6#, or so, boost.  Factory replacement converters are generally lower stall and don't allow the car to build boost.

The factory converter is a lock up unit meaning that there is friction material inside that effectively locks up in third or fourth gears upon command from the ECM and removes the slip inherent in a converter.  This serves to improve fuel mileage and reduce rpm at cruise.

The 12" converters can be restalled to 2600-2800 rpm by bending the blades to a lesser angle inside the converter bent over to parallel the rotation-is this lesser or greater?).  This allows the converter to spin to a higher rpm before the car begins to move.  2800 rpm seems to be considered to be the maximum that a 12" converter should be restalled to before the fin angle becomes such that there is excessive slip all the way thru the rpm band which tends to create too much heat and too much slip at high speed.  Some do sell 12" converters rated to 3000 rpm and depend upon the lock up clutch to handle the slip on the top end.  I don't like these converters as one is asking them to defy the laws of physics and the clutch life is shortened further by locking them up on the strip.

From the factory, the converters do not lock up at wide open throttle.  This is done in the interest of long converter life.  We often mod them by installing a lock up switch, or commanding lock up in the chip, so that we have lock up at wide open throttle.  As we increase the power of the engine, we quickly begin to eat up the clutch in the converter.  I particularly don't like the ECM commanded lock up in daily drivers.  No need to add further abuse on a regular basis to the converter.  I prefer a lock up manual switch.  Then I can decide when to get serious about the abuse.

Back to converter diameter.  When one needs greater stall than 2800 rpm, then one really needs a smaller diameter converter-9", 9.5", or 10" are the common diameters.  The smaller diameter converters obtain higher stalls and better torque multiplication without having to bend the blades as much and this works better on the top end.  The downside to the smaller diameter is greater heat generation and too little clutch area to allow for reliable lock up on a strong engine.

The aftermarket has addressed this problem in various ways, but, the most common  method is to use multiple clutches inside the unit to allow for acceptable clutch area.  Commonly these converters contain 3, 5, or 7 clutches and the price goes up accordingly. 

There are at least three downsides that I can think of with these type converters-Price, Weight, and a Harsh Lockup when cruising down the road and having to frequently lift for traffic.  The unlock, relock can get old very quickly as it jerks the car.  The rotating mass is also quite high and that is not the best either.

For a street driven car, the lock up converters as described above can be very practical.  Better gas mileage and less heat generation which can shorten the tranny life.

The alternative for more strip oriented cars is the non-lockup converter which is similar to what older cars traditionally used.  They are much lighter in weight which reduces rotating mass and they often offer better torque multiplication, not too mention that they are much simpler and reliable.  The downside is slippage throughout the run which may hurt the mph on the top end and they can generate a lot of heat with the continual slippage in normal driving.  All cars should have an external cooler for added tranny longevity, but, the non-lockup units should be equipped with the largest possible. 

Non-lockup converters require a minor pump mod when being installed.

There always has been an ongoing dispute over which is best, lockup, or non-lockup.  I think I prefer non-lockup on cars faster than the lower 11s or strip only cars.  This is opinion based upon a number of years of observation rather than any hard proof.

Stall-how much should I use?  Sometimes I think stall is in the eye of the beholder just like tuning.  First, it is hard to define stall in a turbo car as the turbo itself is such a power modifier that a converter that stalls to X on one car, may far exceed that number on another car.  The turbo characteristics also have a lot to do with it.  Matching turbo to converter is one of the more important items on the list when putting a combo together.

The idea when selecting stall is to be able to quickly obtain enough rpm so that the turbo can then make enough boost at launch to immediately spool to full boost on within a few feet of the starting line.  For street driven cars, one should not have to stand on the brake and gas for several seconds to get to this point...takes the fun out of street fun.

Typically, the factory D5 works well with stock thru TA49/TE44's.  More stall should not be needed if the fueling is correct on the car so that the turbo spools correctly.  So often, people are unhappy because they don't think they can burn the tires off on launch and they go to a higher stall.  Then they find out that while they are spinning their tires, the other guy is driving away from them.

It should be noted that what blows the tires away on the street may not do much at all on a well prepped strip with a set of slicks on the rear. 

Therefore, we always have to consider some compromise and learn to drive the car in all conditions...this may mean less that wide open throttle at launch on the street if the car is equipped with a converter aimed at high boost launches on slicks at the strip.

When foot braking a converter, the quality of the rear brakes, the tires, and the pavement condition has a lot to do with it.  Typically, I find that a converter that will quickly allow 5# of boost on street tires will allow twice that on slicks on a sticky strip.

Recommending stall is a tricky business as ultimate stall depends both on the manufacture of the unit and the hp in the stall range being generated by the car.  When a car fails to achieve the stall rating of the converter, one has to figure out if the car is at fault, or is the problem with the converter.

Typically, I suggest stock stall for a TA49/TE44 and then I suggest dropping down in converter diameter to say a 10" unit for a 3000 rpm stall on a TE60, 3200 for a 61, and then going to a 9 or 9.5 for a 3500 with a TE63, for example.  My best advice is to consult with the turbo supplier and find out what he suggests for the turbo in question.  Dealing with savvy vendors like Jack Cotton, Lawrence Conley, John Craig, etc. will help you get the best advice.  Be wary of those that sell such things but don't have the financial wherewithal to back up their suggestions/products.

Once you have decided upon a stall range, talk to your favorite tranny guy and/or ask on the boards for favorite brands.  I think it is worth buying a good one and preferably one that comes with at least one free restall so you can make an adjustment if it needs a tweak.

Engine Tuning

So Why did I take so long to get to the important stuff?  It's very simple, if your car will not perform consistently from run to run, it makes it much harder to analyze what the engine is doing.  Eliminate the variables in order to understand the constants.  Anyway, drag racing is about getting to the lights first, and the easiest tenths are off the starting line as I initially pointed out.

The Cardinal Rule- Do your best to never change more than one thing before you go out and try to determine how effective that change was.  If you change a number of things, it becomes extremely difficult to determine what caused the change whether it be positive, or negative.

Required equipment

    1.  Intellectual equipment-A basic understanding of how things work.  For instance, if you are running 110 mph at the lights, you are probably making about 400 hp in a Regal (numerous formulas online to calculate hp from speed and weight).  If you read the Basics section on fuel injector sizing, you will know it takes about 0.6 lbs of fuel per hour to support one hp.  Therefore, it takes about 240 lbs/hr of fuel at the level you are running.  If you are running 83 lb injectors , they are theoretically capable of supplying 6 x 83 lbs/hr of fuel to your engine per hour or 498 lbs/hr-----more than twice what you need.  If your chip is only supplying about 50% Duty Cycle at the end of the run, then you know you are in the ball park.  If it is supplying 80%, then you know you have a problem.

Once in the ball park of the above example, one can start tweaking to see if less fuel makes it faster, or does more fuel do it.  It may be that the car is making 400 hp because it is extremely rich and it might be that it would make 450hp if leaned down. Therefore one has to test and tune under as consistent conditions as possible in order to make intelligent decisions based upon changes in basic parameters rather than on changes based upon changes in ambient conditions.

It's not just simple technical things as pointed out above, but how changes in weather, etc. affect hp output.  For example, a change of 20 degs in air temp can effect a change in hp output in the magnitude of 15-20 hp.  This means that such things have to be considered when evaluating tuning changes, and, if at the track, should affect the tuning changes you make to counteract the weather change.

    2.  Required test equipment-At a minimum, you need a recording scan tool (the only one that really fits the bill is Direct Scan as others don't provide enough samples to be meaningful on a quick car), a fuel pressure gauge on a long hose that can be monitored while making a run, an audible knock (detonation) alarm, an Exhaust Gas Temperature gauge (digital preferred), and an analog boost gauge (or an accurate digital model).  An A/F monitor that uses a wideband Oxygen sensor for input can be useful-only if the user does not believe in magic numbers and will do the testing required to determine at what A/F his particular car runs the best.

Now let's consider these items in a bit more detail.

    A. Recording Scan Tool-We need to derive two basic uses from the scan tool.  First, we want to be able to monitor various parameters in order to look for potential anomalies and/or problems.  Secondly, and just as important, if not more important, is the need for the data logging that Direct Scan provides.  Unlike a conventional ALDL scan tool that records data approximately each 1.4 seconds, Direct Scan records up to 18 data sets per second.  This is absolutely necessary if one is to evaluate one run against the next whether one is comparing rpm change during shifts, or searching for voltage aberrations, duty cycle, etc.  One can spend a lot of money on professional data logging equipment, or a lot less for a Scan Tool that will double as a data logger-just be sure it has a high sample rate.

B.  A fuel pressure gauge that can be mounted under a wiper blade on the windshield where it can be read during a run is required to insure that the pump is supplying sufficient fuel during a run.  It is not needed for each and every run, but only periodically to verify that things are okay in the pump department when problems arise.  I prefer to use a large diameter, high accuracy unit from Grainger or McMaster-Carr.

C.  An audible knock alarm with a loud alert as well as visual warnings is a necessity to save you from potential disaster.  No matter what your tuning theories may be, detonation will kill an engine in a matter of moments under high boost conditions.  If the alarm goes off, Lift!

D.  Most Regals seem to run at their best at Exhaust Gas Temps somewhere between 1500-1650 degs.  It's up to you to determine where your car runs the best.  Don't assume that the highest temp without detonation will generate the most hp.  It will take several runs to determine what your car likes.  This depends on probe placement as well as engine combination and fuel quality.

E.  An accurate analog boost gauge, or a high quality digital gauge, is required.  The digital gauges that have a logging function can be very helpful in tracking boost and ensuring that it comes up rapidly and stays where it should be.  Depending upon your particular combination, a pound of boost increment may be worth a tenth of a second in the quarter.  Being able to monitor it accurately is a big help in fine tuning.

F.  Wide band Oxygen sensors that display Air/Fuel ratios can help dial in a combination as long as one does not believe in the magic numbers.  If someone tells you that he set his A/F to something like 11.3/1 in order to be safe, ask him what he did to determine what was dangerous?  Because of the tendency of people to try to come up with so called magic numbers rather than do actual testing in order to determine what it takes to maximize performance, I hesitate to recommend such things.

Mechanical Condition-Yes, I know I am being redundant as I stick this in every section, BUT, if your car is not in proper working condition, you are wasting your time.

If the turbo is blowing oil, the valves are burnt, the tranny is slipping, or flaring between second and third, a cylinder lacks compression, a head gasket is blown, the car detonates under boost, the cam has a flat lobe, and/or the timing chain is wasted, ad nauseam, stay away from the track...fix the damn car!  Otherwise, you have nothing that can be made to perform properly and you are just inviting more expensive repair bills if you try.

Engine Cooling

An old adage states that one-third of the combustion heat goes into making power, one-third goes out the tail pipe, and one-third goes into the cooling system.  Turbo cars try to make use of the heat going out the exhaust to spin the turbo when required.

The one-third that goes into the cooling system heats the oil and the coolant in the block.  We need some heat in both to make the oil work properly and to minimize wear as well as enhance engine efficiency.

Most engineers seem to think that oil should be at least 180 degs in order to burn off condensation and allow the additives to properly clean.  On the other hand, oil temperatures that rise much above 200 degs begin to contribute to thermal breakdown which shortens the life of the oil and its effectiveness as a lubricant.  How high is safe?  I would guess that the curve steepens greatly at 215-220 degs when it comes to oil life. Okay, we can change the oil more frequently, right?  Yes, but.....

The but is that hot oil splashing on the bottoms of the pistons, etc. contributes to detonation.  We do not want 250 deg oil heating up the piston surface and pushing our engine closer to the detonation limit that what it was when we tuned for maximum safe performance on a colder engine.

The factory oil cooler is often discarded after an engine rebuild and not replaced with an alternate cooler.  Many seem to think that the only purpose of the cooler is to prevent coking in the turbo bearings after the engine is turned off by reducing oil temps.  While this has some merit, the factory was also concerned about detonation and realized the need to make the engines as consistent as possible.

If you are not running an oil cooler, go buy the largest one you can find.  I like the B&M style for durability.  The new ones with the fan are expensive but can be more easily mounted without so much regard for external air flow.  Keeping the oil in the 180-200 deg range will not only help preserve the engine life, but, will make the car easier to tune and improve consistency of performance.

The other half of the cooling system involves the circulation of normally water/antifreeze based coolant thru the water passages and radiator. This circulation is designed to cool the cylinder walls and heads primarily.  From the factory, most came with 180 deg thermostats which was the factory compromise between engine life, efficiency, and detonation control.  Most of us have installed 160 deg units which gives us more insurance against detonation, but, probably gives us a bit worse emissions, and may be slightly shorten engine life.  The few comments that I have seen attributed to factory engineers would seem to suggest that life is not seriously shortened, but, few would suggest going any colder.  Anyone that has run a set of loosely fit forged pistons and heard the "slap" on a cold start up understands the importance of running a thermostat and getting the engine up to 160 degs in a hurry....Slap does not do the ring life any good nor the ring grooves on the piston.  The rocking of the piston wears the rings and hurts seal.

Those running original radiators are probably not obtaining nearly as much radiator efficiency as originally provided.  Between the tubes being clogged from coolant precipitates and mineral deposits plus the deterioration of the fin bond to the tubes, the core simply does not perform like it once did.

Now the car may not run too hot down the road in normal driving, but, add some wide open throttle runs through the quarter mile, and, the temperature probably rises more than it should.

In most cases a new, heavy duty, three row core will improve even upon the original core and certainly a big improvement over the original core 18 years later.  Stay away from four row or five row units as the small tubes and additional thickness work against cooling.  By the time air gets to the rear rows, it is already hot and little cooling is performed by them.  Also, these cores also block air flow and that further hurts the cooling, particularly when sitting still.

For consistency in tuning and performance, I would use a modern core, a heavy duty water pump such as the Flow Kooler, and an overdrive pulley to increase water flow further along with the standard 160 deg thermostat with a 3/32" hole drilled thru it to aid in getting all the air out of the system.  Dual fans will help if you are running a front mount intercooler. 

Running distilled water and RMI-25 will provide the best summer time cooling efficiency and will minimize any bearing damage if you blow a head gasket.  Just remember that minimizing bearing damage does not make it okay to drive a car with water in the oil.  It takes a very small amount of water to destroy the lubrication properties of oil.  In the winter, continue to use antifreeze, but, keep adding the RMI-25 as it prevents the antifreeze from leaving silicate precipitates behind in the engine and radiator. Don't use cheap coolant-use Prestone and stay far away from the Dex-Cool orange stuff no matter what your neighbor tells you.  For every person that likes it, there are five people that have bad experiences with it.  And, anyway, you are going to dump it come spring and go with distilled water for superior cooling, right? (Note!  If you live in an area up north where it can freeze at anytime in the summer, don't take the risk!  Run Antifreeze year round.  You should not need the extra cooling performance anyway)  Remember that RMI-25 must be used for the lubricant package as well as its enhanced cooling/cleaning performance.  The Water Wetter that many use does not prevent rust very long in a daily driver.  RMI-25 can be bought cheaply in quart containers which is good for four applications.

An engine which has a bad radiator also probably has a coating of crud built up on the internal water passages of the block and heads and this greatly affects the ability to transfer heat to the coolant.  If this is a hard coating, there is little that can be done to remove it other than a visit to the hot tank when the engine is rebuilt.  Cleaners will remove the slime which helps as does RMI-25. 

It is important to try to cool the engine back down between runs so that this becomes another constant in the tuning process.  It is easy to add a manual switch to the high speed relay so one can cool down the coolant in the radiator as well as idle the engine and circulate the cooler coolant thru the engine and get the temperature back down.

If you install dual fans, retain the factory wiring and relays.  Don't run the risk of either having a manual switch only, or leaving them on all the time.  If you want heavier wiring, then use the factory relays to switch relays coming directly from the battery.  In my car with dual fans, I use one on the low speed circuit and the other on the high speed circuit.

Tuning-What can I change to make my car run up to its potential? 

There are really only two things that you can do to alter the tune of the engine assuming you have addressed all the basics.

    1.  Change the fueling. (Match it to the boost-or vice versa)

    2.  Change the timing.

Before you start changing things, get a spiral notebook, or a logbook made for such things and write down the particulars of each run-temperature, barometric pressure, humidity, wind direction, wind speed, track condition, etc. as well as the performance details.  It's nice to be at a track that gives you info on several waypoints down the track so you can break the run up into segments for analysis.

Make a few runs to dial in your launch technique in order to determine how much boost you can leave at without spinning the tires and how much air pressure is optimum.  At the beginning, this may take a few tries until you get it figured out.  Then it should be a lot easier and quicker.

Finally make two or three runs to obtain some baseline numbers to see if you are running consistently as it is impossible to make decisions on fueling and/or timing parameters if the car does not repeat itself under similar conditions.  Remember that changes in air temperature, barometric pressure, humidity, etc. will affect your performance so try to do your tuning when there is not a lot of change going on.  If the tank has race gas in it-say 112 octane, set the boost to something safe, say 24# (see the octane section below).  Set the EGT gauge to record and hold the maximum temperature observed on the run.  There should not be any timing retard at this level with that gas and that boost..but, if there is, LIFT!  Reduce the boost and try again.

Miles per hour is a better indicator of horsepower than is time as time is affected by launch and track conditions more than miles per hour at the line.  At the beginning, concentrate on improving the mph in the lights and then go back and analyze the waypoint information and see if you can tweak the fueling/timing to improve the waypoint numbers.

Fueling

Tuning for the quarter mile is much simpler than tuning for optimum street driving.  Why?  Because once the car is launched and shifts into second gear, the engine probably does not see an rpm band much wider than 800-1000 rpm.  Saying this another way....we tune for launch and then wide open throttle in second and third over a relatively narrow band whereas for normal driving we use a much broader rpm band when the gas pedal is not on the floor. Fortunately, the ECM will try to correct for errors in non wide open throttle driving if you are using a conventional closed loop chip.

The path we take will depend somewhat on what type of chip we are using.  Conventional chips don't give us many options and we have to test and take notes so we can tell the chip burner what alterations to make to the chip profile in order to effect the changes we desire.  This may take several tries to get it right.  Our only real tool is our ability to vary the fuel pressure via an adjustable fuel pressure regulator.  It also helps to have a very experienced chip maker that is experienced with our particular brand/size of injectors.

Now, think about this.....a chip that is well burned for 21# of boost will most likely be too lean at 26# of boost.  Why?  Turbos compress air and the more boost we run, the more air ends up in the combustion chamber while the fuel delivered remains the same.  Therefore the Air/Fuel ratio gets leaner and detonation occurs.  The converse is also true.  A chip that is tuned for 26# of boost will produce a rich A/F ratio when the boost is turned down.

We can turn the fuel pressure or the boost up, or down,  to some degree to adjust for this variation.

Now, before we start adjusting fueling/boost (or timing), remember one thing.  Detonation is Bad!  If your buddy told you that a little detonation is okay, he probably has not had to change head gaskets, or had to buy a new engine- yet.  The more boost you run, the deadlier, in small amounts, detonation becomes.  Detonation is Bad!  A degree, or two, on the shift to second may be okay, although I would prefer none, but, it must go away immediately after the shift and not linger, or increase.  Detonation not only damages head gaskets, pistons, rings, piston pins, bearings, and the crank, but, it actually slows down the acceleration of the piston as it tries to reverse the direction of the crank when the piston is pushed down against the normal direction.  Just say NO to Detonation.

Look at the EGT recorded on the baseline runs.  If it is relatively low, say 1400 degs, and there was no timing retard, raise the boost one pound and make another run.  Observe the maximum EGT again. If it is still relatively low, say below 1550 degs, then do another iteration with another ONE pound of boost. Continue this until you either hit 1550 degs, or you begin to see a trace of timing retard. Please note that I chose 1550 degs Fahrenheit as an arbitrary number.  Some cars run best at slightly higher temps, but, you will have to find your optimum, safe number by trial and error.

When you see a hint of detonation as evidenced by a slight amount of timing retard, try adding an additional 2# of fuel pressure without changing the boost and see if that makes the timing retard go away and the EGT fall back. 

If there is no longer retard, try adding another pound of boost and repeat the process.  Once you have arrived at the point where adding fuel does not get rid of the timing retard, I would back up one pound of boost below the last point where there was not timing retard in order to have a little margin for error.  Listen to the knock alarm.  If it goes off, Lift!  Give the engine a chance to fight another day.

Ideally, if you have a friendly chipmaker, or you have a programmable chip, you would like to optimize EGT along the entire run so that you get the best performance at each waypoint recorded.  Same principle as above except you check the egt and timing retard at the 330', 660', and 1000' marks if you have that information available to you.

Keep in mind that the hottest EGT, with no timing retard, may not always equate to the highest mph.  Also understand that a stock turbo may be faster at a lower boost because it may be out of its efficiency range on the compressor map-on the other hand, a better intercooler may extend the usable boost range....another reason you have to take some time and try to understand how these cars work.  Therefore, tune to the fastest MPH, not the hottest EGT or the highest boost.  Don't start out with assumptions as to what will work best, test and let your car tell you.

A comment on EGTs-too rich a mixture will make the EGTs rise as well as too lean a mixture.  The stock O2 sensor is pretty much useless for fine tuning, but, it will give you some crude direction.  If the stock O2 is reading 0.840 v, or some other high O2,  and the EGT is reading 1650 degs, it is a good sign that the high temp is coming from too rich a mixture.  If there is no timing retard, turn the boost up, or turn the fuel down.  Remember that no matter how rich the mixture is, there becomes a point where you are going to have detonation so keep your eye on the timing retard, and the knock alarm, and LIFT when you see/hear it.  Also note that if the mixture is extremely rich, you can have rich mixture induced detonation.  See why I say you have to understand and think?

Now, if you have no easy track access, but can find a straight, level road where you are no danger to others, yourself, or in danger of getting a ticket...then you can make some runs and get the EGT's and boost/fuel dialed in.  A three axis accelerometer such as the GTechPro or the Passport can be helpful in this case. Even a 660' (1/8 mile) run will allow a lot of tuning.

Now a comment for those with programmable chips.  One can generally run leaner in first gear than in second, and leaner in second than in third as the load is less in lower gears due to the effect of the tranny gearing as well as the lack of built up heat in the engine at launch.  A leaner mixture spools better and you should be able to pull a bit more power at launch. You can try leaning down the mixture using whichever means your particular chip allows-just stay out of detonation.

http://www.staginglight.com/guide/octane.html

Timing

I am of the opinion that small changes in timing are not as critical as boost/fueling changes.  This is my opinion and not necessarily a fact.  You can make up your own mind through experimentation.

My experience has been that smaller turbos, on race gas, respond better to increased timing that do larger ones.  A stock turbo at 21# of boost may make the most power at 30 degs of timing at wide open throttle.

A TA49/TA44 may do the best at 26# of boost at 26-28 degs of w.o.t. timing and a T63E may work best at 26# at 24 degs.  Larger turbos may make the best power at 22-24 degs and 24# of boost.  This is a very combination dependent subject and I would hesitate to make any claims other than what you determine works the best for you.

On 93 octane, I find that 18-20 degs is the best as a general observation.  My cars have compression ratios in the range of 9-1 and I like 18 degs after some experimentation.  Even with alky injection, I have decided that I like 18 degs.  It might be that with a progressive controller, I could eke out a bit more, but, I don't really think I am losing much with my 63 size turbo.  I did run a bit more with the T and a TE44.

At any rate, I have not found timing to be as critical as boost.  Now, just as one can run leaner in first than in second, etc. so can more timing be used in first than second, etc.

I would suggest that you first try to dial in boost and fueling as described above, then back off boost 2-3# and increase the timing a couple of degrees and see if you can run without detonation.  Compare the times with what you ran at the same boost level with less timing.  Then begin to add boost again until you reach the edge of detonation and back off just as before.  Did you go faster?

With programmable chips, this may be easy to do.  With conventional chips, this can be more time consuming if the chip has to be reburnt each time.

Other Aspects

Data Logging

Even if you have no timing device, you can use Direct Scan's data logs to make some decisions.  If you plot mph versus time you can make some conclusions.  RPM versus time in a given gear can be used for comparing runs as well.  Don't waste your time trying to make use of the hp plots, the A/F plots, etc.  These really don't have any meaningful information.  Input the pertinent data into Excel so you can compare run to run to see what the variation in your tuning actually did.

You can compare miles per hour at the top of third gear against a calculated mph at the same rpm to determine torque converter slippage. 

Keep an eye on voltage for fall off.  The O2s don't mean much, but, gross changes could signal a fuel delivery problem as well as a problem with the chip fuel profile.  Remember that duty cycle is predetermined by the programmer and is not indicative of the engine's need.

Weight

Sometimes it is easier to go faster by removing weight than it is to find speed by tuning.  The Net abounds with formulas to compute the effect of weight variation, horsepower, and speed.  An old rule of thumb was that 100 pounds of weight reduction will knock a tenth off the quarter.  Although it depends upon weight, frontal area, and coefficient of drag, it is probably not far off on our cars.  Therefore, when someone tells you how fast his lightweight, low drag coefficient car is due to his choice of parts, don't forget that the car should be fast as it weighs about 800 lbs less, has about 75% of the frontal area and a drag coefficient about 20% lower and takes about 60 hp less to run 130 mph than does your Regal.  He should be about 1.3 seconds quicker than you when you add it up.  Maybe he is not really making all that much power, but is taking advantage of his choice of platforms?  Again, we must understand what we are comparing before we make decisions.

Removing the front bar and adding a mini-starter (which will knock off  8lb in the right area) are easy things to do.  Unload the trunk, spare tire and all.  That is another place to save a few pounds.

A coat of really slick wax and lowering the car is about all you can do to get it through the air better, but, going on diet for both the car and the owner can add up to significant time reduction and the good thing about it is the reduction of wear and tear on the drive train.

Weather

As I have mentioned several times in this section, weather can have a wide variation upon your performance.  Use this formula to normalize your performance (I suspect it is more accurate for mph than ET as ETs depend a lot upon track prep as well as track temperature).  As the density altitude changes during the day, you can add/subtract fuel and/or boost to help minimize the effect upon your performance which is crucial whether you are bracket racing, or going heads up.

When the density altitude is lower, then the air is more dense and you need more fuel.  If you were running rich, the car will probably pick up miles per hour.  If you were tuned very well and were right on the edge of being lean, the car will probably slow down or begin to detonate and you need more fuel to take advantage of the improving air.

http://www.smokemup.com/auto_math/corr_rel_hum.php

http://www.csgnetwork.com/densaltcalc.html

The first link works if you have relative humidity and the second works if you have the dew point temperature.

Enter your performance along with the weather conditions for each run and compare the normalized results..this will help analyze performance changes under different conditions.

Note that Station Pressure is not the normal barometric pressure that the TV reports.  It is the actual barometric pressure read on site without being normalized to sea level.   Get a cheap digital barometer and set the altitude to zero and it will read station pressure no matter where you are.  Most of the cheap digital barometers will also provide relative humidity and temperature.  If you use dew point, get it from the local weather report via a weather radio, or report off the net for your area.  There are calculators online that will convert the weather report to Station Pressure if you know the pressure in millibars and the altitude in meters.  Bit of pain in the neck so I suggest a cheap digital model.  Ebay is a good source for a Speedtech, or similar, for $50-$100.

As you build your log book data base, you can refer back to similar density altitudes (if you entered them) and find what worked best with regard to fueling and boost.  Takes a little time to accumulate the data but it pays off as it enables you to quickly adjust to current conditions without guessing.  If you are a bracket racer, there are specific packages available that will predict your dial in changes based upon weather conditions as they vary during the day.

Lot's of good math on the above sites.